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A lymphocyte cell surface molecule that is antigenically related to actin
Journal of Immunology (Baltimore, Md. : 1950)
|July 1, 1983
Summary
Researchers identified cell surface actin (CSA) on murine lymphocytes using specific antibodies. This discovery suggests lymphocytes may express actin or actin-related proteins on their surface during development.
Area of Science:
- Immunology
- Cell Biology
- Biochemistry
Background:
- Lymphocytes play crucial roles in immune responses.
- Cell surface proteins are critical for lymphocyte function and recognition.
- The presence and function of actin on the lymphocyte surface remain largely uncharacterized.
Purpose of the Study:
- To investigate the presence and characteristics of actin on the surface of murine lymphocytes.
- To differentiate cell surface actin (CSA) from cytoplasmic actin staining.
- To explore the potential origin and binding characteristics of CSA.
Main Methods:
- Incubation of murine lymphocytes (mesenteric lymph node and thymocytes) with anti-actin antibodies and fluorescent secondary antibodies.
- Distinguishing cell surface staining from cytoplasmic staining using ethidium bromide permeability.
- Analysis of antibody binding via Fc receptor blocking and F(ab')2 fragments.
- Quantification of CSA using flow cytometry and fluorescence microscopy.
- Absorption assays with immobilized actin and IgG-Sepharose.
- Double-labeling experiments to identify CSA-positive cell populations (B cells vs. non-B cells).
Main Results:
- A distinct, punctate surface fluorescence was observed on 52% of MLN lymphocytes and 36% of thymocytes, indicative of CSA.
- CSA staining was clearly differentiated from intense cytoplasmic actin staining in permeable cells.
- Antibody binding to CSA was confirmed not to be Fc receptor-mediated.
- Absorption assays confirmed the specificity of the anti-actin antibody for cell surface-associated actin.
- CSA was detected on approximately 70% of non-B cells and 30% of MLN B cells.
- Preincubation with exogenous actin or MLN supernatant did not increase CSA detection, suggesting no free binding sites.
Conclusions:
- Murine lymphocytes possess detectable cell surface actin (CSA).
- The origin of CSA is likely due to developmentally expressed binding sites or lymphocyte surface expression of actin-related proteins.
- These findings open new avenues for understanding lymphocyte development and function.